This site is not maintained. Click here for the new website of Richard Dawkins.

"Great Dying" Lasted 200,000 Years

Long before the dinosaurs, a bleak environment of widespread fires and oxygen-poor coastal seawater killed off some 90 percent of all Earth's living species. The whole process took less than 200,000 years, according to a new study of the planet's most catastrophic mass-extinction event.

The end-Permian extinction probably isn't as well known as the Cretaceous extinction that wiped out the dinosaurs some 65 million years ago. But the end-Permian collapse nearly spelled the end of life on Earth.

Now scientists have painted a picture of just how fast the "Great Dying" unfolded 252 million years ago.

While the causes of the Permian extinction remain a mystery, from here on out, any theory must be compatible with a 200,000-year time frame centered around 252.28 million years ago, the authors assert. This time span is span indicated by analysis of fossils and chemical evidence of changes in Earth's carbon cycle in rocks from southern China to Tibet.

The two-millennia period is far shorter than the time span that has been widely accepted, according to study co-author Shu-zhong Shen, a paleontologist at the China's Nanjing Institute of Geology and Palaeontology.

The rock and fossil data show that the nightmare scenario for living species unfolded on land and sea simultaneously, said co-author Sam Bowring of the Massachusetts Institute of Technology (MIT).

As of now, Bowring said, "whatever mechanism you invoke [as the cause of the mass extinction] can't be purely marine or purely continental."

Wherever a life-form might have been during the Great Dying, the picture would have been anything but sunny, the researchers say.

"Widespread wildfires played an important role in the rapid deforestation at the end of Permian," said Nanjing's Shen, citing plentiful charcoal-rich and soot-bearing beds found in sedimentary rock of the period.

Rocks also provide hard evidence, via carbon isotope signatures, of oceans under stress as the carbon cycle was reorganized and oxygen levels fell during the Great Dying.

"Marine-organism fossils during the extinction period show a shift from normal species to those who could better tolerate low-oxygen waters," Shen said.

Also, "survivors of the extinction were smaller than the species that came before them—a phenomenon known as the Lilliput effect," after an island home to tiny humans in Gulliver's Travels. This shrinkage is partly attributable to the low oxygen levels, according to Shen.

MIT's Bowring added, "The beauty of those rocks is that we can see what's happening before the extinction event, during the extinction event, and after the extinction—and calibrate it all in absolute time."

Read more

TAGGED: BIOLOGY, EARTH SCIENCES, GENERAL INTEREST


RELATED CONTENT

'Where was God in Aurora?' comments...

Dan Gilgoff - CNN Comments

“A lot of millennials who are coming of age have found that the Internet is a fantastic place to talk about their doubt,” says Jesse Galef, communications director for the Secular Student Alliance.

Update - Twitter exchange - Hard...

First Aid Kit - YouTube -... Comments

First Aid Kit - Hard Believer

Vicar condemns hotel after it replaces...

-- - The Telegraph Comments

Hotel boss Wayne Bartholomew in unrepentant about his new choice of bedside reading for his guests despite an outcry from church authorities.

Sally Ride, first American woman in...

-- - CNN Comments

Sally Ride, the first American woman to fly in space, died Monday after a 17-month battle with pancreatic cancer, her company said. She was 61.

Rbutr finds contrary opinions for...

Tracie Powell - Poynter Comments

rbutr is an application which allows people to follow inter-website debates and easily find and create counter arguments to pages they are viewing.

Pakistani physicist linked to 'God...

AP - CBC News Comments

The pioneering work of Abdus Salam, Pakistan's only Nobel laureate, helped lead to the apparent discovery of the subatomic Higgs boson, or "God particle," last week, but the late physicist is no hero at home, where his name has been stricken from school textbooks.

MORE

MORE BY BRIAN HANDWERK

Halloween 2011: Top Costumes, History,...

Brian Handwerk - National Geographic 32 Comments

Evolution in Action: Lizard Moving From...

Brian Handwerk - National Geographic 17 Comments

MORE

Comments

Comment RSS Feed

Please sign in or register to comment